Selective fusing

ABSTRACT

Fuser regulating methods and the apparatus therefor are provided in accordance with the teachings of the present invention wherein a fuser assembly is selectively energized to obtain variable heating levels in accordance with the intermittent movement of successive portions of a support base through the fuser assembly such that said fuser assembly rapidly attains an operating temperature sufficient to fuse to said support base the electroscopic particles supported thereon. The fuser assembly is energized to a first heating level when successive portions of the support base are moved therethrough within a first time duration. The fuser assembly is energized to a second heating level greater than the first level when a first interval of time has expired since the immediately preceding energization thereof. If a second interval of time has expired since the immediately preceding energization of the fuser assembly, the assembly is energized to a third heating level when the next successive portion of the support base is advanced thereto. The second interval of time is greater than the first interval of time and the third heating level is greater than the second heating level. Further levels of energization may be established in accordance with the amount of time that has expired since an immediately preceding energization.

United States Patent 1 1 Hutner l l 3,745,304 [4 1 July 10, 1973 52 us.01 219/216, 219/388, 250/65 ZE 51 Int. Cl. H05b 3/00 [58] Field 61Search 219/216, 388; 355/9;

263/6 E; 250/65 ZE; 118/637 [56] References Cited UNITED STATES PATENTSI 5/1969 Michaels 219/388 X 8/1968 Tregay et al 219/388 X Primary Examiner-C. L. Albritton Attorney-James J. Ralabate, James C. .langarathiset al.

[57] ABSTRACT Fuser regulating methods and the apparatus therefor areprovided in accordance with the teachings of the cordance with theintermittent movement of successive portions of a support base throughthe fuser assembly such that said fuser assembly rapidly attains anoperating temperature sufficient to fuse to said support base theelectroscopic particles supported thereon. The fuser assembly isenergized to a first heating level when successive portions of thesupport base are moved therethrough within a first time duration. Thefuser assembly is energized to a second heating level greater than thefirst level when a first interval of time has expired since theimmediately preceding energization thereof. If a second interval of timehas expired since the immediately preceding energization of the fuserassembly, the assembly is energized to a third heating level when the'next successive portion of the support base is advanced thereto. Thesecond interval of time is greater than the first interval of time andthe third heating level is greater than the secondheating level. Furtherlevels of energization may be established in accordance with the amountof time that has expired since an immediately preceding energization.

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Pate nted July 10, 1973 4 Sheets-Sheet 2 Patented July 10, 1973 4 Sheets-Sh'eet 4 d l I I l l l l l I IEI I I I I P I I J39 /Z I I I I I I I I II I I I I I II I I I I APIZ I I I I I l I I I I I I I I I I I I I l h sI k E E E I j 1 1 1 x SELECTIVE FUSING This invention relates toelectroscopic fusing techniques and, more particularly, to a method ofselectively regulating a fuser assembly and the apparatus therefor.

Electrophotographic reproducing techniques of the type described indetail in US. Pat. No. 2,297,691 which issued to Chester F. Carlson,form electrostatic latent images of original documents by selectivelydissipating a uniform layer of electrostatic charges deposited on thesurface of a photoreceptor in accordance with modulated radiation imagedthereon. The electrostatic latent image thus formed is developed andtransferred to a support surface to form a final copy of an originaldocument. The' development process is effected by applying electroscopicparticles, conventionally known as toners, to the electrostatic latentimage whereat such particles are electrostatically attracted to thelatent image in proportion to the amount of charge comprising suchimage. Hence, the areas of small charge concentration are developed toform areas of low particle density, while areas of greater chargeconcentration are developed to form areas wherein the particle densityis greater. Once transferred to the support surface, the developed imagemay be permanently fixed thereto by heat fusing techniques wherein theindividual particles soften and coalesce when heated so as to readilyadhere to the support surface.

Various modifications in fusing techniques have heretofore beendeveloped which achieve divers results, such techniques includingselective fusing. In selective fusing, toner areas admitting of a higherdensity are preferentially fused leaving low density or background areasunfused. Unfused toner particles comprising background can then beremoved to yield a cleaner, more readable copy. Selective fusing alsocontemplates the irregular, non-continuous, non-periodic operation of afuser assembly in response to particular predetermined conditions. Inthis regard, selective fusing techniques are readily adapted tocooperate with selective xerographic printing techniques. Thus, ifcopies of only selected ones of successively scanned original documentsare to be printed, the fuser assembly must be energized each time adeveloped image of a selected original is transferred to the supportsurface. It is appreciated that if the support surface comprises a webof suitable material, such as paper, the web will be transported throughthe fuser assembly in an irregular manner corresponding to the scanningof those unique originals to be reproduced. Consequently, scorching orburning of the web that is stationarily disposed within the fuserassembly must be avoided, while, at the same time, sufficient heat mustbe accummulated in the assembly to assure an adequate fusing of thetoner areas to the web.

In the implementation of either of the aforementioned selective fusingtechniques, i.e., the fusing of toner areas of a high density to theexclusion of relatively low density areas on a continuously movingsupport surface or the fixing of successive toner areas disposed inimage configuration upon an irregularly moving support surface, it hasbeen found, that in addition to the problem of scorching the supportsurface, it is necessary to provide for an intrinsic delay in raisingthe temperature of the fuser assembly to a proper value in response tothe energization thereof, the accumulation of heat within the assemblyduring the duration of energization thereof and the temperature to whichthe assembly has cooled in the time that has expired since theimmediately preceding energization thereof. An attendant disadvantage ofprior art selective fusing techniques is the failure of such techniquesto vary the amount of heat emitted by the fuser assembly in accordancewith the length of time such assembly has been permitted to cool. Anattempt to overcome this difficulty has resulted in maintaining thefuser assembly at a quiescent temperature level that, in some instances,has caused the scorching of the support surface disposed therein. Anadvantageous solution to this problem is described in detail incopending application Ser. No. 221193, filed on Jan. 27, 1972, in thename of the instant inventor and assigned to Xerox Corporation, theassignee of the present invention. An alternative solution employing adistinct technique to achieve desirable results is set forthhereinbelow.

Therefore, it is an object of the present invention to provide a methodof and apparatus for selectively fusing electroscopic particles to asupport surface.

It is another object of the invention to provide a method of andapparatus for regulating the operation of a fuser assembly in accordancewith selected conditions requiring the energization of said assemblywherein the heat accumulated by the assembly is a function of theexpiration of time from an immediately preceding energization thereof.

'A further object of the present invention is to provide a method offusing electroscopic particles to successive portions of a support baseintermittently moving through a fuser assembly, and the apparatustherefor.

An additional object of the present invention is to provide apparatusfor selectively energizing a heating element that is maintained at atemperature level no lower than a quiescent level such that said heatingelement is energized to variable heating levels for attaining asubstantially equal average radiant energy level during eachenergization irrespective of the length of time that has expired sincean immediately preceding energization thereof.

Still another object of this invention is to provide a method of rapidlyenergizing a fuser assembly to permit the fixing of toner particlesthereby, while precluding the possibility of scorching a support surfacedisposed therein, and the apparatus therefor.

Yet a further object of the present invention is to provide a method ofselectively energizing a fuser assembly, and the apparatus therefor, inaccordance with the amount of cooling to which said assembly has beensub jected.

Another object of this invention is to provide a method of and apparatusfor fusing electroscopic particles disposed in image configuration on" asupport surface in accordance with the intermittent movement of saidsurface through a fuser assembly.

Various other objects and advantages of the invention will become clearfrom the following detailed description of an exemplary embodimentthereof, and the novel features will be particularly pointed out inconnection with the appended claims.

In accordance with this invention, there are disclosed fuser regulatingmethods and the apparatus therefor, wherein the fuser assembly isselectively energized in accordance with the occurrence of preselectedconditions such that the fuser assembly rapidly attains an operatingenergy level sufficient to fuse to a support surface the electroscopicparticles supported thereon; said fuser assembly being energized to apreestablished heating level when the immediately preceding energizationthereof occurred within a first time duration; and said fuser assemblybeing energized to variable heating levels in accordance with theinterval that has expired since the immediately preceding energizationthereof.

The invention will be more clearly understood by reference to thefollowing detailed description of an exemplary embodiment thereof inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a typical selective printing apparatuswith which the instant invention may be utilized;

FIG. 2 is a schematic diagram of a conventional heating element that maybe utilized in the fuser assembly of FIG. 1 and variable supply ofenergy therefor;

FIG. 3 is a schematic illustration of the logic circuitry that may beutilized to selectively regulate thevariable supply of energy depictedin FIG. 2; and

FIG. 4 depicts a timing diagram representing the voltage signalsproduced by the logic circuit of FIG. 3.

For a general understanding of selective printing apparatus in which theinstant invention may be incorporated, reference is made to FIG. 1 inwhich some of the various system components for the apparatus areschematically illustrated. Like component parts are identified by likereference numerals throughout and primed reference numerals identify thewaveforms produced by corresponding component parts identified byunprimed reference numerals. The printing apparatus illustrated hereinemploys electrophotographic concepts originally disclosed in US. Pat.No. 2,297,691, which issued to Chester F. Carlson. Accordingly, theselective printing apparatus comprises an electrostatic system wherein alight image of an original to be reproduced is projected onto thesensitized surface of a photosensitive plate to form an electrostaticlatent image thereon. Thereafter, the latent image is developed with anoppositely charged developing material comprising electroscopicparticles, known as toner particles, to form a powder imagecorresponding to the latent image on the photosensitive surface. Thepowder image is then electrostatically transferred to a support base towhich it may be fixed by a fusing assembly whereby the powder is causedto adhere permanently to the support surface.

In the illustrated apparatus, visible document information is providedon each of the data cards 1 that are successively transported from afeeder tray 2 to a restack tray 49. The data cards are transported intimed sequence with respect to the operation of the remaining apparatusillustrated herein, and are caused to traverse detecting and scanningstation B and slit exposure device 34 in successive order. Each datacard is additionally provided with precoded information thereon, whichprecoded information is determinative of the selective printing of thevisible document information carried by the card. More particularly, ifthe precoded information scanned from the card by scanning station Badmits of a particular precondition, additional logic circuitry, notshown, responds to such scanned information to derive a print signal.The thus derived print signal is operated upon in a timed sequence toprovide a direct correspondence between the sequential manipulation ofsuch print signal and the particular operation performed by theapparatus illustrated in FIG. 1.

The sequential passage of data cards from the scanning station B throughthe projection system 33 to the restack tray 49 will cause opticalimages of the visible document information on each of the data cardspassing through the slit exposure device 34 to be sequentially projectedupon the surface of photosensitive drum 20. If desired, the projectedimages may admit of magnification. The photosensitive drum 20 iscontinuously driven at a constant angular velocity such that the surfacethereof is moving at a velocity equal to that of the data cards movingpast the exposure device 34. In moving in the direction indicated by thearrow, prior to reaching the exposure station C, that portion of thephotosensitive drum being exposed is uniformly charged by a coronadischarge station G.

The exposure of the photosensitive drum surface to the light imageselectively dissipates the electrostatic charge on the surface thereofin the areas struck by light, thereby forming an electrostatic latentimage in image configuration corresponding to the light image projectedfrom the-visible document information on the data card transportedthroughthe slit exposure device 34. As the photosensitive drum surfacecontinues its movement, the electrostatic image passes through adeveloping station D in which there is positioned a developing apparatusgenerally indicated by the reference numeral 13.

If the electrostatic latent image passing through development station'Dis derived from a data card having a print signal associated therewith,such print signal is utilized to activate the developer motor 24 suchthat the developing apparatus may be operated to develop suchelectrostatic latent image. In contradistinction thereto, should theelectrostatic latent image passing through the developing station D bederived from a data card not having a print signal associated therewith,the developer motor 24 is not activated and such elec-. trostatic latentimage is not developed. It is therefore appreciated that the developingapparatus 13 is operated in an intermittent manner wherein only thoseelectrostatic latent images derived from data cards having print signalsassociated therewith are developed at station D. Hence, as thephotosensitive drum 20 continues to rotate in the direction indicated bythe arrow, successive areas thereof will be provided with imageinformation distributed thereon in the form of a distributedelectrostatic charge pattern. However, only selected ones of successiveareas will be developed. As illustrated herein, the developing apparatus13may typically be provided with electroscopic particles that arecascaded across the surface of photosensitive drum 20, which particlesare attracted electrostatically to the distributed charge pattern toform powder images.

The developed electrostatic image is transported by the photosensitivedrum 20 to a transfer station E located at a point of tangency on thephotosensitive drum whereat a support base 9 is intermittently moved ata speed in synchronism with the moving drum in order to accomplishtransfer of the developed image. The support base 9 is here depicted asa web comprised of suitable material such as paper, plastic or the like,that is driven from a supply 13 through selective transfer mechanism 25,through fuser assembly 40, about strip driving means 16 and into a stripreceiving tray 14. At the time a developed image having a print signalassociated therewith arrives at the transfer station E, the associatedprint signal is operated upon to cause the web driving means 16 to beactivated, thereby transporting the support base 9 at a velocity equalto the surface velocity of the photosensitive drum 20. Moreover, theprint signal is used to operate the selective transfer mechanism 25whereby the support base 9 engages the photosensitive drum 20 in an arcof contact. In addition, charging means 30 may be energized to provide acharge on the support base 9 prior to its engagement with thephotosensitive drum so that the developed image may be electrostaticallytransferred from the surface of drum 20 to the adjacent side of thesupport base as such support base is brought into contact therewith.Thus, it is seen, that each developed electrostatic image is transferredto the support base 9; and the support base is, therefore, advanced inan intermittent manner in accordance with each print signal that isderived from the scanning information carried by the transported datacards.

After transfer, the support base 9 is transported tothe fuser assembly,generally indicated by the reference numeral 40, wherein the developedand transferred powder image on the support base is permanently fixedthereto. The fuser assembly 40 may comprise conventional apparatuscapable of carrying out various fusing techniques such as oven fusing,hot air fusing, radiant fusing, hot and cold pressure roll fixing andfusing and flash fusing. Merely for the purpose of explanation, it willbe assumed that the fuser assembly 40 is comprised of one or more quartzlamps connected in parallel relationship and adapted to emit an amountof heat when energized that is directly related to the magnitude of theenerigzing voltage. The dimensions of the assembly may be such as toadmit of a plurality of transferred images to be disposed therein.Additionally, the fuser assembly is maintained at a quiescent operatingtemperature when not energized, said quiescent operating temperaturebeing slightly less than the temperature normally required to fix thepowder image, to prevent scorching of the support base. It is,therefore, readily apparent that the print signal derived from a datacard is operated upon in a preselected sequential manner incorrespondence with the transporting of a transferred image to the fuserassembly 40. Since, however, immediately succeeding areas of the supportbase 9 are provided with transferred images, but succeeding ones of vthe data cards are not necessarily provided with the unique precodedscanning information, it is recognized that the support base is movedintermittently through the fuser assembly in an irregular manner.Consequently, the fuser assembly 40 must not be continuously energizedin order to avoid the scorching of the support base that is maintainedin a temporary stationary relationship with respect thereto.Nevertheless, as an immediately succeeding portion of the support baseis advanced to the fuser assembly, the latter must be rapidly energizedto an operating level capable of fixing the electroscopic powder imageupon the support base. The manner in which the fuser assembly 40 isregulated to provide the just-mentioned selective fusing is described indetail hereinbelow.

The excess electroscopic particles remaining as residue on the developedimages, as well as those particles not otherwise transferred therefrom,are carried by the photosensitive drum 20 to a cleaning station F on theperiphery of the drum adjacent the charging station G.

The cleaning station may comprise a rotating brush and a coronadischarge device for neutralizing charges remaining on thenontransferred electroscopic particles. Various other configurations andcomponents may comprise the cleaning station F as is well known to thoseof ordinary skill in the art.

A more complete description of the selective printing apparatusillustrated in FIG. 1, and the manner in which such apparatus operates,is set forth in detail in copending application, Ser. No. 221,229, filedon Jan. 27, 1972, by Mark A. Hutner, et al., and assigned to XeroxCorporation, the assignee of the instant invention. It should, however,be clearly understood that the selective fusing techniques to bedescribed in detail hereinbelow are readily adapted for broadapplication and should not be unnecessarily limited to the specificsystem described above. It will, therefore, become readily apparent thatthe instant invention may be readily utilized whenever selected ones oforiginal documents are to be reproduced. Stated otherwise, the selectivefusing techniques described hereinbelow are readily adapted to fixpowder images to a support base therefor on an irregular basis inaccordance with the occurrence of preselected conditions. Thus, inaddition to the selected use as described with respect to FIG. 1, theselective fusing techniques of the present invention may be employed forthe preferential fusing of dense image areas while leaving low densityor background areas unfused.

Turning now to the subject matter of the present invention, and inparticular, to FIG. 2, there is schematically illustrated a conventionalheating element 105 that may be typically included in the fuser assembly40 of FIG. 1. The heating element 105, which may comprise a plurality ofquartz lamps connected in parallel relationship, is coupled'to avariable supply of voltage, generally designated by the referencenumeral 100, the latter being adapted to supply the heating element 105with energy. The variable supply may be a conventional voltage regulatorsuch as model 9T68Y700l manufactured by General Electric, and thereforeneed not be described in detail herein. It should however, be noted thatthe variable supply 100 includes bidirectional current conducting means101 which may be a silicon bi-directional triode device, such as atriac, capable of conducting relatively high AC current in bothdirections and whose time of initial conduction during a half cycle isdependent upon the magnitude of a control voltage applied to the triggerinput 101a thereof. Hence, the bi-directional current conducting means101 may function as a triggerable switch that is rendered conductiveduring a half-cycle of an AC voltage applied thereto when the voltageexceeds a threshold or firing level. Those of ordinary skill in the artwill recognize that the bi-directional current conducting means may be aconventional thyristor. 0nce rendered conductive, the bi-directionalcurrent conducting means 101 is adapted to remain conductive until thevoltage applied thereto commences a successive halfcycle.

It may be observed that the control voltage applied to the trigger input101a of bi-directional current conducting means 101 is derived from avoltage dividing means that comprises series connected resistance means102, 103 and 104. Trigger input 101a is coupled to the junction formedby the series connection of resistance means 102 and 103. The value ofthe resistance the bi-directional current conducting means 101 isrendered conductive, is decreased by selectively reducing the voltagederived by the illustrated voltage dividing means. A plurality ofresistance means 106-108 are capable of being selectively connected inseries relationship with resistance means 102 by energizable shuntingswitch means 106a-108a. Resistance means 106 is greater than resistancemeans 107 which, in turn, is greater than resistance means 108. Inaddition, switch means l06a-108a are capable of being individuallyopened as will soon be seen. It should be appreciated that the effectiveresistance of the first stage of the illustrated voltage dividing meansis increased when one or more of resistance means 106-108 is connectedin series with resistance means 102. Consequently, the threshold orfiring level voltage applied tothe trigger input 101a of bidirectionalcurrent conducting means 101 is correspondingly reduced in accordancewith the total value of series resistance. Thus, the time of initialconduction during a half cycle is advancedand the duration ofconductivity of the bi-directional current conducting means'l01 isincreased. With one or more of resistance means .106-108 connected inseries with resistance means 102, the root mean square (RMS) voltageapplied to heating element 105 is increased proportionally. resulting ina corresponding increase in the amount of heat radiated therefrom.Typically, when shunting switch means 106a is opened to connectresistance means 106, in series withresistance means 102, a maximumfusing voltage is applied to heating element 105 whereby a maximumheating level is obtained thereby. Similarly, when shunting switch means107a is opened to connect resistance means 107 in series with resistancemeans 102, an intermediate fusing voltage is applied to heating element105 whereby an intermediate heating level is obtained thereby. And whenshunting switch means 108:; is opened to connect resistance means 108 inseries with resistance means 102, a minimum fusing voltage is applied toheating element 105 whereby a minimum heating level is obtained thereby.Obviously, additional series connected resistance means may be providedto obtain various other heating levels, a'sdesired.

When 'an energizable'shunting switch means is energized so as to assumean open state, a corresponding resistance means 106-108 is therebyconnected in seties with resistance means 102. It may be recognized thatthe shunting switch means may comprise the movable contacts ofconventional relays, electronic switches or the like. The connecting ofresistance means 106-108 to resistance means 102 alters the ratio ofdivision of the voltage dividing means to thereby alter'the thresholdlevel applied to trigger input 101a. Accordingly, the point at which thebi-directional current conducting means 101 is rendered conductiveduring the positive half cycle of the AC voltage applied thereto isadvanced in accordance with the value of the connected resistance means.The conductivity of the bi-directional current conducting means ismaintained until the conclusion of the positive half-cycle. During thenegative half-cyle of the AC voltage, bi-directional current conductingmeans 101 is rendered conductive at a symmetrical point. The relativelylarge duration of conductivity during each cycle is effective to apply acorrespondingly increased RMS voltage to heating element 105 whereby thelevel of heat radiated by the heating element is sufficient to fuse theelectroscopic material. It should be readily. apparent that variousother switching circuits and associated switch means may be provided toincrease the resistance of the first stage of the voltage dividingmeans, thereby altering the ratio of division thereof in a suitablemanner.

An exemplary embodiment of apparatus that may be utilized to energizeenergizable shunting switch means 10611-10811 is schematicallyillustrated by the logic circuit of FIG. 3 and comprises storage means200, gating means 203, 204 and 205 and driver means 208, 209, 210.Storage means 200 is adapted to store a history of the'precedingenergizations of the heating element includedin the fuser assembly 40illustrated in FIG. 1 and, therefore, may comprise a plural stage shiftregister meansincluding an input terminal for receiving an irregularlyoccurring selective enerigzing signal and a shift terminal for receivinga periodic shift signal. It is recalled that the selective printingapparatus with which the present invention may be utilized is adapted todevelop and transfer an image of a given data card when said card isprovided with scanning information from which is derived a print signal.As described in copending application Ser. No. 221,229, filed Jan. 27,1972, a derived print signal is shifted through shift register means intimed relation with the rotation of image information obtained from acorresponding data card. The image information is distributed on thesurface of a rotating photosensitive drum in the form of a distributedelectrostatic charge pattern. Accordingly, the relative positionof theimage information at any given time may be determinedby the particularposition oc cupied by the print signal as said print signal is shiftedthrough the shift register means. Moreover, once the image informationis developed and transferred to a portion of the support base, themovement of that portion may be represented by a corresponding shiftingof the printsignal through the shift register means. It should,therefore, be readily apparent that a print signal will be shifted to apredetermined position within the shift register means when a portion ofthe support base is advanced to the fuser assembly. I-Ience,electroscopic particles thatare disposed in image configuration on thesupport base are to be fused to the support base when a print signaloccupies said predetermined position. As will soon become apparent, theprint signal occupying the predetermined position need not be associatedwith that particular portion of the support base that is advanced to thefuser assembly, However, except for initial portionsof the support base,each succeeding portion that is transported to the fuser has a powderimage disposed thereon. Storage means 200 may, therefore, comprise aportion of the aforementioned shift register means having a first stagecorresponding to the predetermined position and including a plurality ofsucceeding stages. Alternatively, the storage means 200 maycomprise anindividual plural stage shiftregister means having a first stagecorresponding to the aforementioned predetermined position and includinga plurality of succeeding stages. In either case, the storage means isillustrated in FIG. 3 as comprising a plural stage shift register meanswherein only stages l-8 have been designated as only these stages are ofinterest here. As is understood by those of ordinary skill in the art, aconventional shift register is adapted to shift an input signal appliedthereto consecutively through the stages thereof in accordance with atransition in the shift signal applied. The shift register may,therefore, comprise a counter capable of representing timing informationrelating to the times of occurrence of successive input signals inaccordance with the particular stages occupied thereby.

The input terminal of storagemeans 200 is coupled to terminal 201 towhich is applied a preselected information signal such as theaforementioned print signal. The shift terminal of storage means 200 iscoupled to terminal 202 to which is applied a periodic shift signal. Theperiodic shift signal may be derived from the systern clock which isexplained in detail in copending application Ser. No. 221,229, filedJan. 27, 1972. Accordingly, the periodic shift signal may take the formof clock pulses having a period corresponding to the rate at which thedata cards are scanned and imaged.

The clock pulse period is thus equal to the interval of time required totransfer successive developed images from the photosensitive drum tosupport base 9. Consequently, the clock pulse period is also equal tothe interval of time required to translate successive portions of thesupport base 9 to the fuser assembly 40.

The outputs of stages l-7 of storage means 200 are coupled to theillustrated decoding means, which decoding means is adapted to analyzethe sequence of the print signals that have been supplied to storagemeans 200. The decoding means includes first gating means 203, secondgating means 204 and third gating means 205. First gating means 203 iscomprised of a coincidence means including a first input terminalcoupled to the first stage of storage means 200, a second input terminalcoupled to the output terminal of second gating means 204 and a thirdinput terminal coupled to the output terminal of third gating meand 205.The coincidence means is adapted to sense successive occurrences of aprint signal and the expiration of no more than a preestablishedinterval of time therebetween. Coincidence means 203 is adapted toproduce an output signal in response to the application of apredetermined signal at each input terminal thereof. Accordingly,coincidence means 203 may comprise a conven tional NAND gate whereby abinary 0 is produced at the output terminal thereof when a binary l issupplied to each input terminal thereof. For the purpose of the presentdiscussion, it will be assumed that a binary l is represented by apositive DC potential and a binary 0 is represented by ground potential.It is, of course, understood that the foregoing binary signals may berepresented by any suitable voltage potentials. Similarly, coincidencemeans 203 may comprise a conventional AND gate whereby a binary l isproduced at an output terminal thereof when a binary l is supplied toeach input terminal thereof.

The second gating means 204 is adapted to sense the expiration of afirst interval of time intermediate successive occurrences of a printsignal and to produce a signal in response thereto. More particularly,gating means 204 is adapted to detect when more than two clock pulseperiods, but less than a predetermined number of clock pulse periods,have expired since the occurrence of the immediately preceding printsignal. Such expiration corresponds to an elapsed time since theprevious enerigzation of the heating element included in fuser assembly40 that the fuser assembly has cooled to a temperature requiring ahigher level energization thereof to attain a suitable accumulation ofradiant energy in the assembly. Second gating means 204 includes a firstinput terminal coupled to a given stage, such as the first stage, ofstorage means 200 via inverting means 206, a second input terminalcoupled to a second stage of storage means 200, a third input terminalcoupled to a third stage of storage means 200 and a fourth inputterminal coupled to the output termini of third gating means 205 viainverting means 207. An output signal is produced by second gating means204 when the first stage of storage means 200 is occupied by a printsignal but the second and third stages, respectively, of storage means200 are not occupied by a print signal. Accordingly, second gating means204 may comprise a conventional OR circuit wherein a binary 0 isproduced at the output terminal thereof when a binary 0 is applied toeach input terminal thereof. Alternatively, the second gating means 204may comprise a conventional NOR gate, a NAND gate or an AND gate,wherein a first input terminal thereof is coupled directly to the firststage of storage means 200 and the second and third input terminalsthereof are coupled to the second and third stages, respectively, ofstorage means 200 via inverting means. The inverting means 206 and 207illustrated herein may each comprise a conventional logic negationcircuit adapted to produce a binary 0 in response to a binary l suppliedthereto, and, conversely, to produce a binary l in response to a binary0 supplied thereto.

The third gating means 205 is adapted to sense the expiration of asecond interval of time intermediate successive occurrences of the printsignal, the second interval being greater than the aforementioned firstinterval. More particularly, gating means 205 is adapted to detect whenmore than the aforementioned predetermined number of clock pulse periodshave expired since the occurrence of the immediately preceding printsignal. For the purpose of explanation, it will here be assumed that thepredetermined number is six; however, any other arbitrary number ofclock pulse periods may be selected. Should this condition obtain, it isappreciated that the time that has elapsed since the previousenergization of the heating element included in the fuser assembly 40 issufficient to permit cooling of the fuser assembly to a point whereat amaximum level of energization thereof ispreferred to achieve a suitableaccumulation of radiant energy therein. Gating means 205 may include afirst input terminal coupled to the first stage of storage means 200 viainverting means 206 and second through seventh input terminals coupledto stages 2-7, respectively, of storage means 200. The gating means maycomprise a conventional OR circuit similar to OR circuit 204 or,alternatively, an AND gate, NAND gate, NOR circuit or other suitablegating means. It is recognized that if gating means 205 is constructedof commercially available logic components, a seven-input OR circuitmight not be feasible. Accordingly, the OR circuit may be comprised of apair of readily available four-input OR circuits having output terminalscoupled to a further OR circuit.

Although not specifically illustrated herein, additional gating means,similar to those just described, may be provided to sense the expirationof other intervals of time intermediate the successive occurrences of aprint signal. Similarly, the interconnections between gating means 205and storage means 200 may adopt any suitable configuration to permit thesensing of the expiration of any corresponding interval of time.

The configuration of NAND gate 203, OR circuit 204 and OR circuit 205 isadapted for mutually exclusive operation. Hence, an output signal may beproduced by one and only one of the illustrated gating means at anyinstant of time. This is achieved by utilizing the output signals ofsome of the gating means as inhibit signals to inhibit the operation ofother gating means. More particularly, the output terminal of OR circuit205 is coupled to the input terminals of OR circuit 204 and NAND gate203, respectively, and the output terminal of OR circuit 204 is coupledto another input terminal of NAND gate 203. Consequently, an outputsignal produced by OR circuit 205 serves to inhibit OR circuit 204 andNAND gate 203 from producing output signals; and an output signalproduced by OR circuit 204 serves to inhibit NAND gate 203 fromproducing an output signal.

As illustrated in FIG. 3, the output terminals of NAND gate 203, ORcircuit 204 and OR circuit 205 are coupled to corresponding drivingmeans 208, 209 and 210, respectively. The driving means are conventionalin that each responds .to a binary applied thereto to provide areference potential, such as ground, at its output terminal. The outputterminals of driving means 208, 209 and 210 are coupled to theenergizing coils 108b, l07b and 106b, respectively, of conventionalrelays. It should be recognized that each energizing coil is associatedwith the contact of a switch means 108a, 107a and 106a of FIG. 2. Hence,the energization of a coil effects the opening of a corresponding switchmeans.

Each of driving means 208, 209 and 210 is adapted to respond to a binary0 switch energizing signal applied thereto to supply an associatedenergizing coil with ground potential. Accordingly, driving means 208may comprise a conventional intergrated circuit such as model SN 75451Amanufactured by Texas Instruments, lnc., and having an input coupled toNAND gate 203, and an output to energizing coil 108b. Driving means 209and 210 may be similarly constructed and further description thereof isnot deemed necessary for a sufficient understanding of the presentinvention.

The operation of the apparatus illustrated in FIG. 3 will now bedescribed. It is recalled that the successive portions of the supportbase 9 upon which the electroscopic particles are disposed in imageconfiguration are intermittently moved through the fuser assembly 40even though the .data cards and photosensitive drum are continuallyadvanced and rotated, respectively. Consequently, it is expected that ifone out of five cards, for example, are to be printed, only1one printreceiving portion of the support base 9 will be moved through the fuserassembly 40 during the interval required to process the five data cards.Stated otherwise, only one print signal in the form of a pulse will beapplied to terminal 201 notwithstanding the application of five clockpulses to terminal 202. To facilitate the ready understanding of theinstant invention, the example represented by the timing diagram of FIG.4, as read in a left to right configuration, will be assumed. Thisexample is assumed merely for purposes of illustration and should not beconsidered to unnecessarily limit the instant teachings of the inventionthereto. It will also be assumed that the fuser assembly and printingapparatus operatively associated therewith has been in operation forsome time. At the first timing period under consideration, i.e., attimimg pulse 1 of waveform 202', the first print signal, represented bythe first pulse at the left-hand portion of waveform 201 is applied toterminal 201. It is seen that this first pulse 201 represents that aportion of the support base 9 has been advanced to the fuser assembly40, the heating element included in the fuser assembly must now beenergized to attain a temperature sufficient to achieve the fixing ofthe electroscopic particles to the support base and the heating elementhas not been energized since the last occurrence of the immediatelypreceding pulse 201, not shown. Thus, at clock pulse 1, the print signalis shifted into the first stage of storage means 200 and stages 2-7thereof are not provided with print signals. The storage means 200 maybe responsive to the positive transition of the clock pulses 202 appliedthereto. Of course, the negative transitions of the clock pulses may beutilized to shift applied signals through the storage means, if sodesired. Accordingly, the binary l stored in the first stage of storagemeans 200 is inverted by inverting means 206 and applied as a binary 0to OR circuit 205. Since each of stages 2-7 now stores a binary O theremaining input terminals of OR circuit 205 are each supplied with abinary 0 Consequently, OR circuit 205 produces a binary 0 switchenergizing signal as illustrated by waveform 205, representing that morethan six clock'pulse periods have expired since the occurrence of theimmediately preceding print signal. This switch energizing signal isapplied to NAND gate 203 and OR circuit 204 as inhibit signals. Thus,NAND gate 203 produces a binary l in response to the binary 0 suppliedthereto by OR circuit 205. Similarly, inverter means 207 supplies ORcircuit 204 with a binary 1 whereby a binary l is produced by the latterOR circuit. Waveforms 203' and 204' illustrate the inhibiting of NANDgate 203 and OR circuit 204.

It is thus appreciated that only driving means 210 is supplied with abinary 0 .Consequently, only energizing coil 106b is energized asillustrated by waveform 106b. At clock pulse 1, therefore, current flowsfrom the source of energizing potential +V through energizing coil 106bto ground potential applied to the energizing coilby driving means 210.Switch means 106a is activated, and thereby opened, to connectresistance means 106 in series with resistance means 102. The resistancemeans 106 exhibits the maximum resistance, thereby triggeringbi-directional current conducting means 101' to supply the heatingelement 105 with energizing voltage admitting of a maximum amplitude.Heating element 105 is thus energized to a maximum heating level asindicated by waveform 105. This maximum heating level is preferredbecause it is recognized that the fuser assembly 40 had not beenpreviously energized for a prolonged period of time and the heatingelement therein had cooled to a lower quiescent temperature.Energization of the heating element with a maximum voltage level willpermit the fuser assembly to accumulate additional radiant energywhereby a higher temperature is attained.

It is apparent from waveform 201', that at clock pulse 2 a print signalis not applied to terminal 201. Hence, the next successive portion ofthe support base 9 is not moved through the fuser assembly 40. This, ofcourse, means that the image information derived from the data cardcorresponding to clock pulse 2 is not to be printed. Hence, a binary 0is stored in the first stage of storage means 200 and the print signalis shifted into the second stage thereof. NAND gate 203 is thus suppliedwith a binary O to produce a binary l at the output terminal thereof. ORcircuits 204 and 205 are each supplied with a binary l stored in thesecond stage of storage means 200 to produce a binary l Consequently,none of the driving means 208-210 are supplied with switch energizingsignals and each of the switch means 106a-108a remains closed. Fuserassembly 40 is not energized and the heating element is maintained at aquiescent level. At clock pulse 3, terminal 201 is not provided with aprint signal and, therefore, the fuser assembly 40 need not beenergized. In addition, at this time, the first print signal that hadbeen applied to terminal 201 is shifted into the third stage of storagemeans 200. Similarly, at clock pulse 4, that print signal is shiftedinto the fourth stage of storage means 200.

Waveform 201' indicates that the next successive print signal pulse isapplied to terminal 201 during clock pulse period 5. At this time, theimmediately preceding print signal is shifted into the fifth stage ofstorage means 200. Hence, if each clock pulse period is assumed to be332 milliseconds, approximately 1,328 milliseconds (i.e., four clockpulse periods) have elapsed since a given portion of the support base 9was moved into the fuser assembly 40. Moreover, approximately 996milliseconds have elapsed since the energization of the heating elementof the fuser assembly 40 was terminated. The fuser assembly has,therefore, cooled such that the accumulated energy therein hasdissipated below the fusing level. At clock pulse 5, the immediatelypreceding print signal is shifted into the fifth stage of storage means200 to supply OR circuit 205 with a binary l It is apparent that thecondition precedent to the production of a switch energizing signal byOR circuit 205 has not been fulfilled. The OR circuit responds to thebinary 1 supplied thereto to apply a binary 0., via inverter means 207,to OR circuit 204 and to apply a binary I to NAND gate 203. It is notedthat the elapsed time between successive print signals has exceeded twoclock pulse periods. The second and third stages of storage means 200are not provided with print signals and, therefore, each of the inputterminals of OR circuit 204 coupled to the second and third stages issupplied with a binary Now, the print signal stored in the first stageof storage means 200 is subject to a logic negation by inverter means206 and is supplied to OR circuit 204 as a binary 0 Consequently, eachinput terminal of OR circuit 204' is provided with a binary 0 resultingin the production of a binary 0 at the output terminal thereof as may beobserved from waveform 204'. NAND gate 203 is supplied with the binary 0produced by OR circuit 204, whereby the operation of the NAND gate isinhibited as indicated by waveform 203'. Consequently, driving means 209is provided with a binary 0 whereas driving means 208 and 210 are eachprovided with a binary l At clock pulse 5, OR circuit 204 produces aswitch energizing signal whereby coil l07b is energized as denoted bywaveform 107b. Switch means 1070 is thus activated to connect resistancemeans 107 in series with resistance means 102. Heating element 105 issupplied with an intermediate voltage amplitude, as represented bywaveform 105, and is energized to an intermediate heating level. Theelectroscopic particles disposed on the support base 9 in imageconfiguration are thus fused to the support base. Furthermore, theintermediate energizing level of the heating element is sufficient toenable the fuser assembly to attain a desirably high temperature, thusaccumulating an adequate amount of radiant energy.

A print signal is not applied to terminal 201 at the next clock pulseperiod 6 and, therefore, further movement of the support base 9 isinterrupted. Thus, that portion of the support base that was previouslyadvanced into the fuser assembly 40 remains therein and the accumulatedradiant energy serves to properly complete the fusing operation. Inaddition, at clock pulse 6, a binary 0 is shifted into the first stageof storage means 200 and the previous print signal is shifted into thesecond stage of storage means 200. Accordingly, NAND gate 203, ORcircuit 204 and OR circuit 205 are each disabled and thus do not produceoutput signals.

The next succeeding print signal is applied to terminal 201 at clockpulse 8 and is shifted into the first stage of storage means 200 asindicated by the waveform 201'. Hence, three clock pulse periods haveelapsed since the immediately preceding print signal was applied toterminal 201 and approximately 664 milliseconds have elapsed since theenergization of the heating element included in the fuser assembly wasterminated. At clock pulse 8, the immediately preceding print signal isshifted into the fourth stage of storage means 200 and the first printsignal is shifted into the eighth stage of storage means 200.Accordingly, OR circuit 205 is inhibited from producing a binary 0switch energizing signal because of the binary l supplied-thereto by thefourth stage of storage means 200. Moreover, the binary 1 produced bythe OR circuit is inverted by inverter means 207 and applied as a binary0 to OR circuit 204. In addition, since the elapsed time betweensuccessive print signals exceeds two clock pulse periods, OR circuit 204is supplied with a binary O by each of the second and third stages ofstorage means 200. Finally, the print signal stored in the first stageof storage means 200 is inverted by inverter means 206 and applied to ORcircuit 204 as a binary O Consequently, the OR circuit produces a binary0 switch energizing signal as depicted by waveform 204', which switchenergizing signal is coupled to and serves to inhibit NAND gate 203.Driving means 209 responds to the switch energizing signal appliedthereto to energize coil 107b, as indicated by'waveform 107b.Energization of coil l07b serves to activate switchmeans 107a to connectresistance means 107 in series with resistance means 102. Heatingelement is thus supplied with an intermediate voltage amplitude and isenergized to an intermediate heating level. The fuser assembly is thusenabled to attain a desirable temperature whereby an adequate amount ofradiant energy may be accumulated. Consequently, the electroscopicparticles disposed in configuration upon the third successive portion ofthe support base 9 are fused thereto.

At clock pulse 9 an immediately succeeding print signal is applied toterminal 201, thereby representing that the support base 9 is advancedthrough fuser assembly 40 to expose the next successive portion of thesupport base to a fusing operation. It is, therefore, appreciated thatthe image information derived from consecutive data cards are to beprinted. Hence, at clock pulse 9 the first and second stages of storagemeans 200 are each occupied by a print signal, the fifth stage ofstorage means 200 is occupied by a print signal and the remaining stagesof storage means 200 are not provided with print signals. At this time,the binary l stored in the second stage of storage means 200 iseffective to inhibit OR circuits 204 and 205 from producing respectivebinary 0 switch energizing signals. It is, therefore, appreciated thateach OR circuit supplies NAND gate 203 with a binary 1 enabling the NANDgate to respond to the signal applied to the remaining input terminalthereof. The print signal applied to terminal 201 and stored in thefirst stage of storage means 200 is applied as a binary 1 to NAND gate203. Consequently, the NAND gate is activated to produce a binary 0switch energizing signal in response to the binary 1 applied to eachinput terminal thereof, as illustrated by waveform 203'. Driving means208 responds to the switch energizing signal applied thereto by NANDgate 203 to energize coil 108b, as represented by waveform 108b'. Theenergized coil activates switch means 108a to open, thereby connectingresistance means 108 in series with resistance means 102. It is recalledthat a minimum energizing voltage is applied to heating element 105 whenresistance means 108 is connected to resistance means 102. This isdepicted by waveform 105'. Hence, a minimum heating level is obtained bythe fuser assembly. The successive energizations of the heating elementis sufficient to apply an adequate amount of heat to the electroscopicparticles disposed in image configuration on support base 9 to fuse saidparticles to the support base. Hence, it is not necessary to energizethe heating element to a level greater than said minimum heating level.The printed images derived from the successive data cards are suitablyfixed to the support base to form permanent copies thereof.

At clock pulse 10, the immediately preceding print signal is shiftedinto the second stage of storage means 200, the next preceding printsignal is shifted into the third stage of storage means 200 and the nextpreceding print signal is shifted into the sixth stage of storage cedingprint signal, the fourth stage of storage means 200 is occupied by thenext preceding print signal and the seventh stage of storage means 200is occupied by the third preceding print signal. Since the elapsed timebetween successively occurringprint signals does not exceed two clockpulse periods, only NAND gate 203 producesan output signal, representedby waveform 203'. The signal produced by NAND gate 203 is applied as aswitch energizing signal to driving means 208. Consequently, coil. 108bis energized and switch means 108a is activated to thereby connectswitch means 108 in series with switch means 102. Thus, the heatingelement 105 included in the fuser assembly 40 is energized to a minimumheating level as represented by waveform 105'. Electroscopic particlesare thus fused to the intermittently moving support base.

During the next succeeding clock pulse periods, the

image information rotating on the photosensitive drum is not printedand, therefore, a print signal pulse is not applied to terminal 201, thesupport base 9 is not advanced through the fuser assembly 40 and theheating element included in the fuser assembly is not energized.However, at clock pulse 18 image information derived from a data cardand transferred to the support base 9 is to be fixed to the supportbase. Accordingly, a portion of the support base upon whichelectroscopic particles are disposed in image configuration is advancedto the fuser assembly 40 and a print signal is applied to terminal 201and shifted into storage means 200 as represented by waveform 201. Noneof the second to seventh stages of storage means 200 is occupied by aprint signal. It is recognized that more than two clock pulse periodshave expired since the occurrence of the immediately preceding printsignal. In fact, more than six clock pulse periods have'expired. Thus,heating element 105, which has cooled to a lower quiescent temperature,must be energized with a maximum voltage to enable sufficient radiantenergy to accumulate in the fuser assembly 40. Consequently, OR circuit205 receives a binary 0 from each of the second through seventh stagesof the storage means 200, as well as a binary 0 from inverter means 206.A binary 0 switch energizing signal is thus applied to driving means 210by the OR circuit as illustrated by waveform 205'. Moreover, the switchenergizing signal serves to inhibit OR circuit 204 and NAND gate 203from producing their respective switch energizing signals in the nowunderstood manner. Therefore, coil 106b is energized to activate switchmeans 106a, resulting in the supply of a maximum amplitude energizingvoltage to heating element 105, as indicated by waveform 105. It isappreciated that the fuser assembly isthus energized to a maximumheating level.

It should now be fully appreciated from the foregoing descriptionthereof that storage means 200 stores the time related history of themovement of successive portions of support base 9 through the fuserassembly 40.

Clearly, a variable time interval may elapse between consecutivemovements. This, of course, is represented by the selected stages ofstorage means 200 which are occupied by print signals. Moreover, sincethe energization of the heating element of the fuser assembly isdependent upon the application of a print signal to terminal 201, theselected stages of storage means 200 that are occupied by print signalsprovide an indication of the-length of time that has expired betweensuccessive energizations of the heating element.

In the description of FIG. 3, it has been assumed that conventional,commercially available TTL logic is utilized throughout for each of theNAN D gates, OR circuits, inverting means, storage means and drivingmeans. However, any of the specific logic components or arrangments maybe replaced by other components or groups thereof which produce similaroutput signals in response to corresponding input conditions. Also, theprecise mode of logic operation employed thereby may differ from thatdescribed hereinabove in a manner that is obvious to those of ordinaryskill in the art. Furthermore, the logic circuit illustrated in FIG. 3may, alternatively, be implemented by MSI logic, individual circuitcomponents or MOS circuit chips. In addition, the variable supplyillustrated in FIG. 2 may be replaced by other conventional sources ofenergy sufficient to supply the heating element with variable voltagesin response to the switch energizing signals produced by the NAND gate203, OR circuit 204 and OR circuit 205 of FIG. Accordingly, suitablehigh voltage sources may be selectively and/or permutatively coupled toheating element 105 through conventional switching means, the latterbeing adapted to be activated in response to the switch energizingsignals produced by the aforementioned gating means. Although discreteenergy levels are illustrated as being applied to the fuser assembly, itis appreciated that energy admitting of a continuous function may beapplied. Moreover, the heating element 105 need not be limited merely toa conventional quartz lamp, but, alternatively, may comprise anysuitable heat radiating device or other heating device conventionallyutilized in fuser assemblies or other electroscopic particle fixingdevices.

In the embodiment illustrated in FIGS. 2 and 3, the activation of switchmeans 1060-10811 and, therefore, the operation of gating means 205, 204and 203, respectively, need not be mutually exclusive. Accordingly,resistance means 106-108 may all be equal and the operation of thegating means to produce corresponding switch energizing signals will addadditional resistance to the voltage dividing means. Thus, the operationof NAND gate 203 need not be inhibited by OR circuits 204 and 205 and,similarly, the operation of OR circuit 204 need not be inhibited by ORcircuit 205. Hence, if NAND gate 203 produces a switch energizing signalupon detecting successive occurrences of a print signal, resistancemeans 108 is connected to resistance means 102 and the fuser assembly isenergized to its minimum heating level. If more than two clock pulseperiods have expired between successive print signals, both OR circuit204 and NAND gate 203 may produce switch energizing signals to connectresistance means 107 and resistance means 108 to resistance means 102.The fuser assembly is then energized to its intermediate heating level.And if more than six clock pulse periods have expired between successiveprint signals, then OR circuit 205, OR circuit 204 and NAND gate 203 mayproduce switch energizing signals to connect all of resistance means106-108 to resistance means 102. The fuser assembly is then energized toits maximum heating level.

While the invention has been particularly shown and described withreference to an exemplary embodiment thereof, it will be obvious tothose skilled in the art that various changes and modifications in formand details may be made without departing from the spirit and scope ofthe invention. Thus, the specific numerical examples describedhereinabove are intended to be merely illustrative of the operation ofthe apparatus disclosed herein and are not intended to limit theteachings of the instant invention. Accordingly, any suitable clockpulse period may be employed herewith. Moreover, storage means 200 maycomprise any conventional storage device capable of storing a suitablehistory of the previous operation of the fuser assembly and, therefore,of the intermittently moving support base. OR circuit 204 may be adaptedto produce a switch energizing signal if three or more clock pulseperiods have expired since the occurrence of the immediately precedingprint signal. Similarly, OR circuit 205 may be adapted to produce aswitch energizing signal when any other convenient number of clock pulseperiods have expired since the occurrence of an immediately precedingprint signal. And additional gating means may be provided to producefurther switch energizing signals upon detecting the expiration of otherclock pulse periods. It is, of course, recognized that these OR circuitsand gating means may, therefore, produce switch energizing signals toenergize the heating element of the fuser assembly to a suitable heatinglevel in accordance with the particular interval of time that hasexpired since the immediately preceding energization of the heatingelement. In addition, resistance means 106-108 may be replaced with anactive element having a variable resistance dependent upon the magnitudeof an applied voltage, such as a voltagecontrolled resistor FETtransistor, a silicon offset-gate depletion-type MOS transistor, or thelike. The control voltage applied to the variable resistance may bederived by summing the switch energizing signals produced by the gatingmeans of FIG. 3. It is, of course, recognized that in this modification,the operation of the gating means is not mutually exclusive.Accordingly, the total number of gating means that are activated and,therefore, the magnitude of the control signal derived, is a function ofthe expiration of time intermediate successive print signals. Moreover,the voltage that is thus applied to the heating element need not admitof discrete levels, as illustrated in FIG. 4, but may, if desired, be acontinuously varying amplitude. It is intended that the appendedclaims-be interpreted as including the foregoing as well as otherobvious changes and modifications.

What is claimed is 1. A method of regulating the operation of a fuserassembly in accordance with selected information requiring theenergization of said fuser assembly wherein the radiant energyaccumulated by said fuser assembly is a function of the expiration oftime from an immediately preceding energization thereof, comprising thesteps of:

sensing the occurrence of a preselected information signal to energizesaid fuser assembly to a preestablished minimum energy level; and

energizing said fuser assembly to a variable energy level that isdependent upon the interval of time that has expired intermediatesuccessive occurrences of said preselected information signal.

2. The method of claim 1 wherein said fuser assembly is energized uponsensing the respective occurrences of the succeeding ones of thesucceeding ones of the successive preselected information signals.

3. The method of claim 2 wherein said step of sensing the occurrence ofa preselected information signal comprises the steps of:

serially storing each preselected information signal and the number ofpredetermined time durations separating successive ones of saidpreselected information signals in consecutive order; and

generating a fuser energizing signal when a preselected informationsignal is stored in a first position of said consecutive order.

4. The method of claim 3 wherein said step of energizing said fuserassembly comprises the step of generating a variable amplitude fuserenergizing signal when a preselected information signal is stored in afirst position of said consecutive order and a number of predeterminedtime durations are stored in the next successive positions of saidconsecutive order, said fuser energizing signal admitting of anamplitude that is a func- I tion of said number of successively storedpredetermined time durations.

5. A method of regulating the operation of a fuser assembly inaccordance with selected information requiring the energization of saidfuser assembly wherein the heat accumulated by said fuser assembly is afunction of the expiration of time from an immediately precedingenergization thereof, comprising the steps of:

serially storing each preselected information signal and the number ofpredetermined time durations separating successive ones of saidpreselected information signals in consecutive order; generating a firstswitch energizing signal when a preselected information signal is storedin a first position of said consecutive order;

generating a second switch energizing signal when a preselectedinformation signal is stored in a first position of said consecutiveorder and a'first selected number of predetermined time durations arestored in the next successive positions of said consecutive order;

generating a third switch energizing signal when a preselectedinformation signal is stored in a second position of said consecutiveorder and a second selected number of predetermined time durations arestored in the next successive positions of said consecutive order; and

selectively energizing said fuser assembly to first, second and thirdenergy levels in response to said first, second and third switchenergizing signals, respectively.

6. The method of claim wherein said fuser assembly is energized to aminimum energy level when said first switch energizing signal isgenerated, said fuser assembly is energized to a second energy levelgreater than said minimum energy level when said second switchenergizing signal is generated and said fuser assembly is energized to athird energy level greater than said second energy level when said thirdswitch energizing signal is generated.

7. Apparatus for regulating the fusing of electroscopic particles tosuccessive portions of a support base intermittently moving through afuser assembly wherein said fuser assembly includes a source of thermalradiation coupled to a variable supply of voltage, comprising:

switch means included in said variable supply and adapted when energizedto apply a variably increased voltage to said source of thermalradiation from said variable supply to increase the heat radiated bysaid source whereby said electroscopic particles are fused to saidsupport base; and

means for selectively energizing said switch means for applying avoltage admitting of a selectively variable amplitude to said source ofthermal radiation when a portion of said support base is moved throughsaid fuser assembly, said selectively variable amplitude being afunction of the interval of time that has expired since an immediatelypreceding portion of said support base was moved through said fuserassembly.

8. The apparatus of claim 7 including storage means for storing the timerelated history of the movement of successive portions of said supportbase through said fuser assembly, said storage means being coupled tosaid means for selectively energizing said switch means.

9. The apparatus of claim 8 wherein said storage means comprises:

shift register means including an input terminal to which is applied asignal representing the movement of a portion of said support basethrough said fuser assembly; and

means for continually shifting on a periodic basis each signal appliedto said input terminal through said shift register means whereby therelative positions occupied by signals within said shift register meansis a function of the history of the movement of said support basethrough said fuser assembly.

10. The apparatus of claim 9 wherein said means for selectivelyenergizing comprises:

first means for energizing said switch means to apply a voltageadmitting of a minimum amplitude to said source of thermal radiationwhen successive portions of said support base are moved through saidfuser assembly within a first duration;

second means for energizing said switch means to apply a voltageadmitting of a second amplitude, greater than said minimum amplitude, tosaid source of thermal radiation when a portion of said support base ismoved through said fuser assembly at a time later than the expiration ofa first interval of time after an immediately preceding portion is movedtherethrough; and

third means for energizing said switch means to apply a voltageadmitting of a third amplitude, greater than said second amplitude, tosaid source of thermal radiation when a portion of said support base ismoved through said fuser assembly at a time later than the expiration ofa second interval of time after an immediately preceding portion ismoved therethrough, said second interval of time being greater than saidfirst interval of time.

11. The apparatusof claim 10 wherein said first means comprises firstgating means coupled to the'first position of said shift register meansfor producing a first switch energizing signal when said first positionis occupied by a signal.

12. The apparatus of claim 11 wherein said second means comprises secondgating means coupled to the first position of said shift register meansand to a first preselected number of successive positions of said shiftregister means for producing a second switch energizing signal when saidfirst position is occupied by a signal and none of said firstpreselected number of successive positions is occupied by a signal.

13. The apparatus of claim 12 wherein said third means comprises thirdgating means coupled to the first position of said shift register meansand to a second preselected number of successive positions of said shiftregister means for producing a third switch energizing signal when saidfirst position is occupied by a signal and none of said secondpreselected number of successive positions is occupied by a signal.

14. The apparatus of claim 13 wherein said first, second and thirdgating means are coupled to first, second and third switches,respectively, included in said variable supply, said first switch beingresponsive to said first switch energizing signal to apply said minimumamplitude voltage to said source of thermal radiation, said secondswitch being responsive to said second switch energizing signal to applysaid second amplitude voltage to said source of thermal radiation andsaid third switch being responsive to said third switch ener gizingsignal to apply said third amplitude voltage to said source of thermalradiation.

15. The apparatus of claim 14 wherein said variable supply includesbidirectional current conducting means supplied with an AC voltage, saidbidirectional current conducting means being initially conductive at apoint in the half-cycle of said AC voltage that is a function of acontrol voltage applied thereto such that an increase in said controlvoltage tends to advance the initial conductive point and a decrease insaid control voltage tends to retard the initial conductive point, saidcontrol voltage being selectively increased in response to theenergization of said first, second and third switches, respectively.

16. Apparatus for regulating the fusing of electroscopic particles tosuccessive portions of a support base intermittently moving through afuser assembly wherein said fuser assembly includes a source of thermalradiation coupled to a variable supply of voltage, comprising:

variable resistance means included in said variable supply and adaptedwhen energized to apply a variably increased voltage to said source ofthermal radiation from said variable supply to increase the heatradiated by said source whereby said electroscopic particles are fusedto said support base; and

means for selectively varying said variable resistance means forapplying a voltage admitting of a selectively variable amplitude to saidsource of thermal radiation when a portion of said support base is movedthrough said fuser assembly, said selectively variable amplitude being afunction of the interval of time that has expired since an immediatelypreceding portion of said support base was moved through said fuserassembly.

17. The apparatus of claim 16 including storage means for storing thetime related history of the movement of successive portions of saidsupport base through said fuser assembly, said storage means comprising:

shift register means including an input terrnainl to which is applied asignal representing the movement of a portion of said support basethrough said fuser assembly; and means for continually shifting on aperiodic basis each signal applied to said input terminal through saidshift register means whereby the relative positions occupied by signalswithin said shift register means is a function of the history of themovement of said support base through said fuser assembly. 18. Theapparatus of claim 17 wherein said means for selectively varyingcomprises:

first means for varying said variable resistance means to apply avoltage admitting of a minimum amplitude to said source of thermalradiation when successive portions of said support base are movedthrough said fuser assembly within a first duration;

second means for varying said variable resistance means to apply avoltage admitting of a second amplitude, greater than said minimumamplitude, to said source of thermal radiation when a portion of saidsupport base is moved through said fuser assembly at a time later thanthe expiration of a first interval of time after an immediatelypreceding portion is moved therethrough; and

third means for varying said variable resistance means to apply avoltage admitting ofa third amplitude, greater than said secondamplitude, to said source of thermal radiation when a portion of saidsupport base is moved through said fuser assembly at a time later thanthe expiration of a second interval of time after an immediatelypreceding portion is moved therethrough, said second interval of timebeing greater than said first interval of time.

19. In combination with a heating element that is maintained at atemperature level no lower than a quiescent level of temperature, saidheating element radiating an amount of heat that is dependent upon thelength of time expired between successive energizations thereof,apparatus for selectively energizing said heating element to variableheating levels such that a substantially equal radiant energy level isattained thereby during each energization irrespective of the length oftime that has expired since an immediately preceding energizationthereof, comprising:

energizing means coupled to said heating element for supplying saidheating element with variable magnitudes of energy;

storage means for storing signals representative of the history of theselective energization of said heating element; first means coupled tosaid storage means and responsive to a selective energizing signal forenergizing said heating element to a minimum heating level when theimmediately preceding energization of said heating element occurredwithin a first time duration; second means coupled to said storage meansand responsive to a selective energizing signal for energizing saidheating element to a second heating level, greater than said minimumheating level, when a first interval of time has expired since theimmediately preceding energization of said heating element; and

third means coupled to said storage means and responsive to a selectiveenergizing signal for energizing said heating element to a third heatinglevel, greater than said second heating level, when a second interval oftime has expired since the immediately preceding energization of saidheating ele ment.

20. The combination of claim 19 wherein said storage means comprisesplural stage shift register means including an input terminal forreceiving an irregularly occurring selective energizing signal and ashift terminal for receiving a periodic shift signal, whereby thesignals applied to said'input terminal are shifted through said pluralstages in timed relation such that the relative positions occupied byselective energizing signals is a function of the previous energizationsof said heating element.

21. The combination of claim 20 wherein said first, second and thirdmeans comprise first, second and third gating means coupled to first,second and third switch means, respectively; said first gating meansincluding an input coupled to a first stage of said shift register meansfor producing a first switch energizing signal when a selectiveenergizing signal is shifted into said first stage, said second gatingmeans including an input coupled to said first stage of said shiftregister means and inputs coupled to a first preselected number ofsuccessive stages of said shift register means for producing a secondswitch energizing signal when a selective energizing signal is shiftedinto said first stage and none of said first preselected number ofsuccessive stages receives a selective energizing signal, said thirdgating means including an input coupled to said first stage of saidshift register means and inputs coupled to switch means being responsiveto said second switch energizing signal for activating said energizingmeans to supply said heating element with a second magnitude of energyand said third switch means being responsive to said third switchenergizing signal for activating said energizing means to supply saidheating element with a third magnitude of energy.

1. A method of regulating the operation of a fuser assembly inaccordance with selected information requiring the energization of saidfuser assembly wherein the radiant energy accumulated by said fuserassembly is a function of the expiration of time from an immediatelypreceding energization thereof, comprising the steps of: sensing theoccurrence of a preselected information signal to energize said fuserassembly to a pre-established minimum energy level; and energizing saidfuser assembly to a variable energy level that is dependent upon theinterval of time that has expired intermediate successive occurrences ofsaid preselected information signal.
 2. The method of claim 1 whereinsaid fuser assembly is energized upon sensing the respective occurrencesof the succeeding ones of the successive preselected informationsignals.
 3. The method of claim 2 wherein said step of sensing theoccurrence of a preselected information signal comprises the steps of:serially storing each preselected information signal and the number ofpredetermined time durations separating successive ones of saidpreselected information signals in consecutive order; and generating afuser energizing signal when a preselected information signal is storedin a first position of said consecutive order.
 4. The method of claim 3wherein said step of energizing said fuser assembly comprises the stepof generating a variable amplitude fuser energizing signal when apreselected information signal is stored in a first position of saidconsecutive order and a number of predetermined time durations arestored in the next successive positions of said consecutive order, saidfuser energizing signal admitting of an amplitude that is a function ofsaid number of successively stored predetermined time durations.
 5. Amethod of regulating the operation of a fuser assembly in accordancewith selected information requiring the energization of said fuserassembly wherein the heat accumulated by said fuser assembly is afunction of the expiration of time from an immediately precedingenergization thereof, comprising the steps of: serially storing eachpreselected information signal and the number of predetermined timedurations separating successive ones of said preselected informationsignals in consecutive order; generating a first switch energizingsignal when a preselected information signal is stored in a firstposition of said consecutive order; generating a second switchenergizing signal when a preselected information signal is stored in afirst position of said consecutive order and a first selected number ofpredetermined time durations are stored in the next successive positionsof said consecutive order; generating a third switch energizing signalwhen a preselected information signal is stored in a second position ofsaid consecutive order and a second selected number of predeterminedtime durations are stored in the next successive positions of saidconsecutive order; and selectively energizing said fuser assembly tofirst, second and third energy levels in response to said first, secondand third switch energizing signals, respectively.
 6. The method ofclaim 5 wherein said fuser assembly is energized to a minimum energylevel when said first switch energizing signal is generated, said fuserassembly is energized to a second energy level greater than said minimumenergy level when said second switch energizing signal is generated andsaid fuser assembly is energized to a third energy level greater thansaid second energy leveL when said third switch energizing signal isgenerated.
 7. Apparatus for regulating the fusing of electroscopicparticles to successive portions of a support base intermittently movingthrough a fuser assembly wherein said fuser assembly includes a sourceof thermal radiation coupled to a variable supply of voltage,comprising: switch means included in said variable supply and adaptedwhen energized to apply a variably increased voltage to said source ofthermal radiation from said variable supply to increase the heatradiated by said source whereby said electroscopic particles are fusedto said support base; and means for selectively energizing said switchmeans for applying a voltage admitting of a selectively variableamplitude to said source of thermal radiation when a portion of saidsupport base is moved through said fuser assembly, said selectivelyvariable amplitude being a function of the interval of time that hasexpired since an immediately preceding portion of said support base wasmoved through said fuser assembly.
 8. The apparatus of claim 7 includingstorage means for storing the time related history of the movement ofsuccessive portions of said support base through said fuser assembly,said storage means being coupled to said means for selectivelyenergizing said switch means.
 9. The apparatus of claim 8 wherein saidstorage means comprises: shift register means including an inputterminal to which is applied a signal representing the movement of aportion of said support base through said fuser assembly; and means forcontinually shifting on a periodic basis each signal applied to saidinput terminal through said shift register means whereby the relativepositions occupied by signals within said shift register means is afunction of the history of the movement of said support base throughsaid fuser assembly.
 10. The apparatus of claim 9 wherein said means forselectively energizing comprises: first means for energizing said switchmeans to apply a voltage admitting of a minimum amplitude to said sourceof thermal radiation when successive portions of said support base aremoved through said fuser assembly within a first duration; second meansfor energizing said switch means to apply a voltage admitting of asecond amplitude, greater than said minimum amplitude, to said source ofthermal radiation when a portion of said support base is moved throughsaid fuser assembly at a time later than the expiration of a firstinterval of time after an immediately preceding portion is movedtherethrough; and third means for energizing said switch means to applya voltage admitting of a third amplitude, greater than said secondamplitude, to said source of thermal radiation when a portion of saidsupport base is moved through said fuser assembly at a time later thanthe expiration of a second interval of time after an immediatelypreceding portion is moved therethrough, said second interval of timebeing greater than said first interval of time.
 11. The apparatus ofclaim 10 wherein said first means comprises first gating means coupledto the first position of said shift register means for producing a firstswitch energizing signal when said first position is occupied by asignal.
 12. The apparatus of claim 11 wherein said second meanscomprises second gating means coupled to the first position of saidshift register means and to a first preselected number of successivepositions of said shift register means for producing a second switchenergizing signal when said first position is occupied by a signal andnone of said first preselected number of successive positions isoccupied by a signal.
 13. The apparatus of claim 12 wherein said thirdmeans comprises third gating means coupled to the first position of saidshift register means and to a second preselected number of successivepositions of said shift register means for producing a third switchenergizing signal when said first position is occupied by a signal andnoNe of said second preselected number of successive positions isoccupied by a signal.
 14. The apparatus of claim 13 wherein said first,second and third gating means are coupled to first, second and thirdswitches, respectively, included in said variable supply, said firstswitch being responsive to said first switch energizing signal to applysaid minimum amplitude voltage to said source of thermal radiation, saidsecond switch being responsive to said second switch energizing signalto apply said second amplitude voltage to said source of thermalradiation and said third switch being responsive to said third switchenergizing signal to apply said third amplitude voltage to said sourceof thermal radiation.
 15. The apparatus of claim 14 wherein saidvariable supply includes bidirectional current conducting means suppliedwith an AC voltage, said bidirectional current conducting means beinginitially conductive at a point in the half-cycle of said AC voltagethat is a function of a control voltage applied thereto such that anincrease in said control voltage tends to advance the initial conductivepoint and a decrease in said control voltage tends to retard the initialconductive point, said control voltage being selectively increased inresponse to the energization of said first, second and third switches,respectively.
 16. Apparatus for regulating the fusing of electroscopicparticles to successive portions of a support base intermittently movingthrough a fuser assembly wherein said fuser assembly includes a sourceof thermal radiation coupled to a variable supply of voltage,comprising: variable resistance means included in said variable supplyand adapted when energized to apply a variably increased voltage to saidsource of thermal radiation from said variable supply to increase theheat radiated by said source whereby said electroscopic particles arefused to said support base; and means for selectively varying saidvariable resistance means for applying a voltage admitting of aselectively variable amplitude to said source of thermal radiation whena portion of said support base is moved through said fuser assembly,said selectively variable amplitude being a function of the interval oftime that has expired since an immediately preceding portion of saidsupport base was moved through said fuser assembly.
 17. The apparatus ofclaim 16 including storage means for storing the time related history ofthe movement of successive portions of said support base through saidfuser assembly, said storage means comprising: shift register meansincluding an input terminal to which is applied a signal representingthe movement of a portion of said support base through said fuserassembly; and means for continually shifting on a periodic basis eachsignal applied to said input terminal through said shift register meanswhereby the relative positions occupied by signals within said shiftregister means is a function of the history of the movement of saidsupport base through said fuser assembly.
 18. The apparatus of claim 17wherein said means for selectively varying comprises: first means forvarying said variable resistance means to apply a voltage admitting of aminimum amplitude to said source of thermal radiation when successiveportions of said support base are moved through said fuser assemblywithin a first duration; second means for varying said variableresistance means to apply a voltage admitting of a second amplitude,greater than said minimum amplitude, to said source of thermal radiationwhen a portion of said support base is moved through said fuser assemblyat a time later than the expiration of a first interval of time after animmediately preceding portion is moved therethrough; and third means forvarying said variable resistance means to apply a voltage admitting of athird amplitude, greater than said second amplitude, to said source ofthermal radiation when a portion of said support base is moved throughsaid fuSer assembly at a time later than the expiration of a secondinterval of time after an immediately preceding portion is movedtherethrough, said second interval of time being greater than said firstinterval of time.
 19. In combination with a heating element that ismaintained at a temperature level no lower than a quiescent level oftemperature, said heating element radiating an amount of heat that isdependent upon the length of time expired between successiveenergizations thereof, apparatus for selectively energizing said heatingelement to variable heating levels such that a substantially equalradiant energy level is attained thereby during each energizationirrespective of the length of time that has expired since an immediatelypreceding energization thereof, comprising: energizing means coupled tosaid heating element for supplying said heating element with variablemagnitudes of energy; storage means for storing signals representativeof the history of the selective energization of said heating element;first means coupled to said storage means and responsive to a selectiveenergizing signal for energizing said heating element to a minimumheating level when the immediately preceding energization of saidheating element occurred within a first time duration; second meanscoupled to said storage means and responsive to a selective energizingsignal for energizing said heating element to a second heating level,greater than said minimum heating level, when a first interval of timehas expired since the immediately preceding energization of said heatingelement; and third means coupled to said storage means and responsive toa selective energizing signal for energizing said heating element to athird heating level, greater than said second heating level, when asecond interval of time has expired since the immediately precedingenergization of said heating element.
 20. The combination of claim 19wherein said storage means comprises plural stage shift register meansincluding an input terminal for receiving an irregularly occurringselective energizing signal and a shift terminal for receiving aperiodic shift signal, whereby the signals applied to said inputterminal are shifted through said plural stages in timed relation suchthat the relative positions occupied by selective energizing signals isa function of the previous energizations of said heating element. 21.The combination of claim 20 wherein said first, second and third meanscomprise first, second and third gating means coupled to first, secondand third switch means, respectively; said first gating means includingan input coupled to a first stage of said shift register means forproducing a first switch energizing signal when a selective energizingsignal is shifted into said first stage, said second gating meansincluding an input coupled to said first stage of said shift registermeans and inputs coupled to a first preselected number of successivestages of said shift register means for producing a second switchenergizing signal when a selective energizing signal is shifted intosaid first stage and none of said first preselected number of successivestages receives a selective energizing signal, said third gating meansincluding an input coupled to said first stage of said shift registermeans and inputs coupled to a second preselected number of successivestages of said shift register means for producing a third switchenergizing signal when a selective energizing signal is shifted intosaid first stage and none of said second preselected number ofsuccessive stages receives a selective energizing signal; and said firstswitch means being responsive to said first switch energizing signal foractivating said energizing means to supply said heating element with afirst magnitude of energy, said second switch means being responsive tosaid second switch energizing signal for activating said energizingmeans to supply said heating element with a second magnitude of energyand said third switch means being responsive to said third switchenergizing signal for activating said energizing means to supply saidheating element with a third magnitude of energy.